Author Topic: RFM95 vs RFM69  (Read 4451 times)

gokr

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RFM95 vs RFM69
« on: April 13, 2017, 11:02:07 AM »
Hi all!

I am planning the hw components of a sensor system. The system consists of a "main" station that typically could be a MEGA (although I am thinking an ESP32 instead) with a LoRa RFM95. The main station should regularly report using LoRaWAN.

Then there are smaller "slave" nodes that would be situated within 20m, typically doing sensor work and transmitting this to the main station. Initially I felt RFM69 between the main and the nodes would be ideal, but that would mean the main station needs both an RFM69 and an RFM95 to do the LoRaWAN communication.

Another approach is to use RFM95 only, both in main and in slaves, thus eliminating one radio chip in the main station. Thus my question. know so far that RFM69 has hw encryption, higher speeds, larger payloads, much better library support. And of course, RFM95 has a much larger reach but in this case that's not interesting.

If the RFM69 is better from a consumption viewpoint that is important since we want the slaves to run for at least 1 year on 2AA (typically). Thus, the automatic output power "down scaling" I read about sounds great.

Any views on this? I am leaning towards using RFM69 between the nodes and an extra RFM95 for the LoRaWAN uplink.

regards, Göran

joelucid

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Re: RFM95 vs RFM69
« Reply #1 on: April 13, 2017, 04:03:52 PM »
The rfm95 includes a full FSK Modem similar though better than the rfm69hw. I think you could use rfm69hw's for the nodes and a rfm95 for the gw and have that normally listen to the nodes using FSK and communicate consolidated data up via LoRa occasionally.

But this setup requires some custom coding.

gokr

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Re: RFM95 vs RFM69
« Reply #2 on: April 14, 2017, 05:37:25 AM »
Ok, that however sounds a bit above my paygrade ;) I am a good programmer, but I am a total n00b when it comes to radio. But its fun stuff!

Do you have any comment on the idea of using ONLY RFM95 for all communication? That would entail the main unit to alternatively use it in plain p2p mode to talk with the slaves - and then use LoRaWAN (LMIC lib I guess) to talk upstream.

regards, Göran

joelucid

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Re: RFM95 vs RFM69
« Reply #3 on: April 14, 2017, 06:02:47 AM »
Quote
Ok, that however sounds a bit above my paygrade ;) I am a good programmer, but I am a total n00b when it comes to radio. But its fun stuff!

I bet you could just port the RFM69 lib fairly easily to use the FSK part of the RFM95. Then use RH or whatever when speaking LoRa.

Quote
Do you have any comment on the idea of using ONLY RFM95 for all communication? That would entail the main unit to alternatively use it in plain p2p mode to talk with the slaves - and then use LoRaWAN (LMIC lib I guess) to talk upstream.

Sure that could work, too. I don't know much about the LoRaWAN protocol though - but I'd expect that it doesn't require being in RX all the time, so you could switch between both.

A draw-back of LoRa is that it doesn't support very high bitrates. And the price. For 20m type distances a RFM69W at -18dBm at 300kbit would easily do the trick. No need for LoRa whatsoever.

Joe